THE EFFICIENT OPHTHALMOLOGIST

Tear osmolarity testing: a new weapon for dry eye

This may be a test whose time has come.

By Steven M. Silverstein MD, FACS

Steven M. Silverstein, MD, FACS, is a corneatrained comprehensive ophthalmologist in practice at Silverstein Eye Centers in Kansas City, Mo. He invites comments. His e-mail is ssilverstein@silversteineyecenters.com. Disclosure: Dr. Silverstein is a speaker for TearLab.

As corneal specialists, we have been limited principally to subjective testing of the spectrum of dry eye disease in an effort to determine its underlying etiology and recommend an appropriate, customized treatment regimen.

For decades, we have depended upon Schirmer’s testing, tear break-up time, staining patterns with lisamine green and fluorescein, inspection of the lid margin and function, and testing corneal sensation with the Cochet-Bonnet esthesiometer. Until recently, testing tear osmolarity was sufficiently complex and expensive as to be limited to laboratory study, though its role in dry eye disease has been known for more than 25 years.

GETTING TO ROOT CAUSES

Our understanding of dry eye diseases has expanded significantly over the last decade and, as such, we now have new treatment methods available with others under investigation. These new therapies are directed specifically toward the most likely cause of a patient’s symptoms. No longer is treatment limited to aqueous deficiency and replacement, as we now focus on infectious, nutritional, inflammatory and environmental factors, as well as relationships with systemic disease and anatomic mediators of the dry eye cascade.

Testing for tear osmolarity with the TearLab system. The result is a number that indicates if dry eye disease is present and, if so, its severity.

A HUGE PATIENT BASE

We know that patients presenting with clinical signs and symptoms of dry eye disease make up the largest demographic of patients seeking eye care, and that despite our careful clinical exam and subjective testing, mostly trial and error have guided our treatment once we’ve compensated for obvious contributors, such as lid margin disease.

Dry eye-related conditions affect both patient comfort and quality-of-vision concepts. These concepts are particularly important in this era of corneal-based refractive surgery, cataract surgery with femto laser incision and premium channel IOLs (particularly multifocal lenses).

Dry eye disease is multi-factoral and each component has an important relationship with tear osmolarity. Though aqueous supplementation is our typical, kneejerk, first line of therapy, more patients with dry eye symptoms have underlying Meibomian gland dysfunction than pure aqueous deficiency. Clinical signs and subjective symptoms often poorly correlate if not conflict, and do a limited job establishing disease severity or response to therapy. In the end, we are just relieved when patients report they feel better.

WHY WE TEST TEAR OSMOLARITY

We know from studies that hyperosmolarity damages the ocular surface. Hyperosmolarity induces apoptosis in human corneal epithelial cells, and causes inflammation. Hyperosmolarity upregulates inflammatory markers such as HLA-DR, a glycoprotein, and MMP-9, a non-specific inflammatory protein.

Many studies, for example, the Beaver Dam, Women’s Health and Blue Mountain studies, have attempted to document the extent of dry eye disease, each of which have underestimated it’s prevalence. Studies Tearlab (San Diego) conducted at 126 US sites with nearly 9,000 patients have helped establish a scale for understanding low, normal, or elevated states of osmolarity and the role in dry eye disease of varying etiologies.

Typically, tear osmolarity should approximate normal blood osmolarity (280-295 mOsml/L). Tear osmolarity greater than 308 mOsml/L is linked to different subsets of dry eye patients. Further, greater differences in the inter-eye measurements (OD vs. OS) and variations in a range of testing times/dates also correlate with severity of disease.

VISUAL FUNCTION AND OSMOLARITY

Osmolarity data correlates well with visual function, as well as with tear-film instability. Objectively, hyperosmolarity and inter-eye variability document disease severity and return to normal with proper treatment. We know, for example, that hyaluronic acid reduces tear osmolarity and that osmolarity stabilizes after treatment with cyclosporine A (Restasis, Allergan, Irvine, Calif.) in appropriate patients. Patients on preservative-free glaucoma medications may also have lower tear osmolarity as well.

A TEST I HAVE FOUND BENEFICIAL

Given these facts, I find it worth noting that Tearlab has developed an affordable in-office technology that quickly and easily documents tear osmolarity. This test helps guide me toward determining the particular contributors to a patient’s symptomatology and enables me to effectively institute a customized treatment protocol.

By obtaining pre- and post-treatment measurements, I can use osmolarity to objectively monitor improvement or disease progression and correlate with patient symptoms and our other testing benchmarks. It is now considered standard of care as an objective marker of disease severity and treatment success or failure in most FDA and phase 4 studies examining new dry eye treatment opportunities.

THE TESTING PROCESS

Osmolarity testing is easy to perform, is 510k-cleared and Clinical Laboratory Improvement Amendments-waived. It requires only 50 nL of sample, and is safe to perform with its “lab-on-chip” technology. This method of testing was the winner of 2009 Medical Design Excellent Award, and is listed in the AAO Preferred Practice Patterns. It has its own CPT code ­(83861), can be billed to a patient’s medical (not vision) plan and requires no co-pay or CMS deductible. The test must be medically necessary and physician-ordered.

REIMBURSEMENT POLICIES

In 2014, CMS will reimburse the test at $22.54 in all 50 states. Commercial insurance reimbursement will depend on your provider contract and may vary among payers. Some third-party payers may not have established a policy for reimbursing code 83861. Providers should contact their regional payers to determine their current reimbursement policies.

I have a Tearlab device in each technician’s work-up lane so they do not forget or skip the test. Similar to knowing their IOPs, patients enjoy tracking their tear osmolarity results once they begin treatment. OM